Premises and Equipment, Net (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 601,957	$ 587,096
Accumulated depreciation and amortization	(310,777)	(288,153)
Total premises and equipment, net	291,180	298,943
Depreciation and amortization	24,400	21,100	$ 19,500
Land
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	78,116	80,519
Buildings
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	210,012	211,923
Leasehold improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	73,405	70,314
Furniture and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 240,424	$ 224,340